1. Field of the Invention
The present invention relates to an information processor and information processing method, adapted to receive and decrypt an encrypted content data and encrypted content decryption key, and control copy of the content data.
2. Description of Related Art
Conventionally, telephone lines, satellite broadcasting circuits, etc. are used for two-way data communication and one-way data communication between a data transmitter and receiver. To prevent data from being leaked to a third party, the data is encrypted for transmission and reception between the data transmitter and receiver. The data thus transmitted and received include content data. The content data further include works such as a piece of music, image, program, text, etc. for example.
Copy of one of content data such as music, image, etc. for which a copyright is reserved will infringe the copyright in some cases even if the copied data is intended for personal use. Copying a digital data without any additional processing made of the data, namely, so-called digital copy or digital dubbing, can provide a content data with no signal deterioration even after such data copy through many generations. Therefore, such data copy has to be inhibited by some method. For example, SCMS (serial copy management system) is known in which such a copy is allowed for only one generation. In this system, an SCMS copy control code is added to or buried in a xe2x80x9cparentxe2x80x9d content data recorded on a CD (compact disc) and it has a value for permission of copy for only one generation, while a xe2x80x9cchildxe2x80x9d content data obtainable at a destination apparatus by digital copy of the xe2x80x9cpatentxe2x80x9d content data at the destination apparatus, has the SCMS copy control code thereof rewritten to a value for copy inhibition.
Generally for serving, by electronic distribution, of a content data such as music data over an Internet or satellite communication system, the content data is encrypted by a key (content key) and the content key used for the data encryption is also encrypted by another key (distribution key).
In case it is permitted as ever to copy a content data such as a piece of music for one generation, a copy control code for a xe2x80x9cparentxe2x80x9d content data should have a value for copy of the content data for one generation but a xe2x80x9cchildxe2x80x9d content data obtainable at an destination apparatus by digital copy of the xe2x80x9cpatentxe2x80x9d content data at the destination apparatus should have a copy control code thereof rewritten to a value for copy inhibition.
For sending an encrypted xe2x80x9cparentxe2x80x9d content to a destination apparatus capable of decrypting such an encrypted content data, it is desirable from the standpoints of a shorter processing time and labor saving to send the content data as it is (without being decrypted) to the destination apparatus. In this case, however, since a copy control code such as SCMS code has also been encrypted along with the content data or it has been buried in the content data, it will be supplied to the destination apparatus without being changed in value. On the contrary, if a content data having a copy control code rewritten to a value for copy inhibition and buried therein is sent to a destination apparatus, the content data has to be decrypted and copy control code has to be rewritten to a value for copy inhibition, and then the content data has to be encrypted again, which will need much labor and time.
Accordingly, the present invention has an object to overcome the above-mentioned drawbacks of the prior art by providing an information processor and information processing method, adapted to control, by a simple operation, copy of a content data transmitted to a destination apparatus.
The above object can be attained by providing an information processor comprising, according to the present invention:
means for receiving an encrypted content decryption key generated by encrypting, by a distribution encryption key, a content decryption key for decryption of a content data encrypted by a content encryption key;
means for decrypting, by a distribution decryption key, the received encrypted content decryption key;
means for encrypting the content decryption key decrypted by the decrypting means and a copy control code by an encryption key which can be decrypted at an external apparatus; and
means for transmitting to the external apparatus the content decryption key encrypted by the encrypting means and the encrypted copy control code.
Also the above object can be attained by providing an information processing method comprising, according to the present invention, the steps of:
means for receiving an encrypted content decryption key generated by encrypting, by a distribution encryption key, a content decryption key for decryption of a content data encrypted by a content encryption key;
means for decrypting, by a distribution decryption key, the received encrypted content decryption key;
means for encrypting the content decryption key decrypted by the decrypting means and a copy control code by an encryption key which can be decrypted at an external apparatus; and
means for transmitting to the external apparatus the content decryption key encrypted by the encrypting means and the encrypted copy control code.
Further, in addition to the reception of the encrypted content decryption key and transmission of the encrypted content decryption key with the copy control code, the encrypted content data is received and the received encrypted content data is transmitted to the external apparatus.
Furthermore, the content encryption key and content decryption key should preferably be a common key for an encryption by a common key encryption system and the distribution encryption key be preferably be a public key for a public key encryption system while the distribution decryption key should preferably be a secret key for a public key encryption system. The encryption key which can be decrypted at the external apparatus and the decryption key should be a common key for the common key encryption system.
Moreover, prior to the transmission by the transmitting means to the external apparatus of the encrypted content decryption key and encrypted copy control code, a mutual authentication should preferably be made between the transmitting means and external apparatus. The encryption key which can be decrypted at the external apparatus and the corresponding decryption key should preferably be a session key generated at the time of the mutual authentication, and shared by the source and external apparatuses.